Spray drying of polymer-containing dispersions, water-in-oil emulsions and water-in-oil microemulsions, and dry polymer products formed thereby

ABSTRACT

Processes for spray drying water-soluble and water-swellable vinyl-addition polymer-containing dispersions, emulsions and microemulsions to obtain substantially dry water-soluble or water-swellable polymer particles, compositions of substantially dry water-soluble or water-swellable polymer particles, methods of agglomerating spray-dried polymer particles, and methods of using sprayed polymer particles and agglomerates in water-treating, mining, paper, food processing, soil conditioning, solution thickening, biotechnological, and oil recovery applications are disclosed.

This application is a continuation of application Ser. No. 09/338,148,filed Jun. 23, 1999, now abandoned which is in turn a continuation ofapplication Ser. No. 08/670,194, filed Jun. 21, 1996, now U.S. Pat. No.6,011,089, which is in turn a continuation-in-part of application Ser.No. 08/479,057, filed Jun. 7, 1995 now U.S. Pat. No. 6,080, 804.

FIELD OF THE INVENTION

This invention relates generally to processes for spray dryingdispersions, emulsions and microemulsions containing water-soluble orwater-swellable polymers to obtain substantially dry water-soluble orwater-swellable polymer particles, compositions of substantially drywater-soluble or water-swellable polymer particles, and methods of usingsaid polymer particles in water-treating, mining, paper,biotechnological, food processing, soil conditioning, solutionthickening, and oil recovery applications.

BACKGROUND OF THE INVENTION

High molecular weight, water-soluble and water-swellable polymersproduced from such monomers as acrylamide are commercially importantmaterials. These polymers find use as flocculants for mining operationsto recover ore from slurries, water treating to remove suspendedimpurities etc., in agriculture as soil conditioners, and also in papermaking to aid paper formation and in oil recovery industries.

Water-soluble and water-swellable polymers are generally commerciallyavailable in solution, dry, dispersion, water-in-oil emulsion, andwater-in-oil microemulsion forms. In many cases polymer solutions areconvenient, but may be limited to low molecular weight polymers and/orlow solids levels because of the problem of handling viscous solutionsof high solids, high molecular weight polymers. At very high solidsand/or molecular weights, the solutions form gels that can be comminutedto form fine polymer gel particles that may be dissolved into water bythe end-user. Although these comminuted gels typically contain up toabout 20% water, they are frequently called “dry” polymers todistinguish them from the other product forms. In many cases the drypolymers exhibit long dissolution times and poor handlingcharacteristics e.g. dusting. Although some handling problems may bemitigated by agglomeration see e.g. EP 0 277 018 A2; U.S. Pat. Nos.3,279,924; 3,275,449, 4,696,762; 5,171,781; both solutions and gels ofwater-soluble and water-swellable polymers may also suffer from the lackof a convenient method for post-reacting or functionalizing the polymer.

Another problem relates to blends of dry polymers, particularly whenblending dry polymers having different particle sizes or particle sizedistributions. It is well known that dry polymer particles tend tostratify on handling and storage, with the larger particles tending tosettle towards the bottom of the container, and the smaller particlestending to be concentrated towards the top. Stratification may beinconvenient because differences in handling characteristics areencountered as a function of container depth. The stratification problemmay be exacerbated when two different dry polymers are blended together,because the particle size distributions of the two products aregenerally not identical. Stratification on storage may affect blendproduct performance as the top of the container tends to become enrichedin the polymer having the smaller particle size. For obvious reasons,changes in product performance as a function of storage depth are to beavoided, and it is generally preferred that each polymer be of similarparticle size, see e.g. EP 479 616 A1 and U.S. Pat. No. 5,213,693.However, when producing dry polymer by spray-drying, changes inproduction e.g. changes in dryer size, dryer temperature, bulk viscosityof the feed, atomizer type, etc. may affect particle size, and it may bedifficult or impossible to achieve a desired particle size whilesimultaneously maintaining some other production parameter, so blends ofspray-dried polymers may be adversely affected by stratification.

The advent of water-in-oil emulsion and water-in-oil microemulsion formsof water-soluble and water-swellable polymers solved some of theseproblems, e.g. blends of water-in-oil emulsions and water-in-oilmicroemulsions as disclosed in U.S. Pat. Nos. 5,883,181 and 5,763,530 donot tend to stratify, and high solids, high molecular weight, andrelatively fast dissolution times may all be obtained simultaneously. Inaddition, unique finctionalized polymers may be produced that cannot bepractically manufactured by polymerization in solution. For instance,U.S. Pat. Nos. 4,956,399; 4,956,400; 5,037,881; and 5,132,023, teachthat functionalization of a water-soluble polymer contained in awater-in-oil microemulsion can be carried out to produce high molecularweight charged polymers with advantageous flocculation performance. Theuse of microemulsions, as opposed to emulsions, in polymer productionprovides improved polymer performance properties among other benefits.Hydrolyzed polyacrylamides with uniquely high molecular weight aredisclosed in U.S. Pat. No. 5,286,806. In U.S. Pat. No. 4,767,540, veryhigh molecular weight hydroxamate-functionalized polyacrylamide isdisclosed, and novel charged organic polymer microbeads are disclosed inU.S. Pat. Nos. 5,274,055 and 5,167,766. In addition, methods foresterifying (meth)acrylic acid polymer and, optionally, hydroxamatingsaid polymers are disclosed in U.S. Pat. No. 5,847,056.

Despite the many benefits provided by emulsion and microemulsionpolymers, transportation costs associated with such materials remainhigh and disposal of the oil and emulsifier in the emulsions may poseenvironmental concerns as secondary pollution. Moreover, many emulsionand microemulsion polymers tend to exhibit stability problems, e.g.detrimental changes in polymer properties and/or performance as afunction of time. Although U.S. Pat. Nos. 5,883,181 and 5,763,530; andU.S. Pat. Nos. 4,956,399; 4,956,400; 5,037,881; 5,132,023; 5,274,055;and 5,167,766 mention non-solvent precipitation and stripping as methodsof recovering dry polymer products from water-swellable or water-solublepolymer microemulsions or microemulsions containing blends, thesemethods may produce a dry polymer with undesirable handling properties,poor dissolution times, low bulk density, etc. Practically, non-solventprecipitation and stripping may be inconvenient and expensive.

Water-soluble polymers may also be prepared in the form of suspensionsor dispersions of polymer beads or droplets in a non-aqueous liquid e.g.oil. The reverse phase polymerization process described in U.S. Pat. No.4,528,321 is said to form dispersions of water-soluble polymers.Water-soluble polymer dispersions, which may be azeotropically dried,are disclosed in U.S. Pat. No. 4,628,078. U.S. Pat. No. 4,506,062discloses a reverse phase suspension polymerization process for theproduction of high molecular weight, water-soluble polymers and alsoreports that dry polymer beads may be obtained by azeotropic evaporationfollowed by filtration. However, a problem remains in that azeotropicdistillation tends to be energy-intensive, and the filtering process maybe hazardous or inconvenient.

Although dry polymers may be obtained from vinyl-additionpolymer-containing water-in-oil emulsions, water-in-oil microemulsionsor dispersions by such methods as precipitation in a non-solvent,stripping, etc., these methods may also be impractical for economic andenvironmental reasons because of difficulties in recovering, purifyingand recycling the oil. Although the oil recovered from an emulsion orsuspension polymerization may occasionally be recycled without furtherpurification, as disclosed in U.S. Pat. No. 4,212,784 and JP 50-124979,in other cases e.g. S.I.R. H915 additional purification steps arenecessary. The level of impurities in the oil is an importantconsideration, as certain polymerizations e.g. chain-growthpolymerizations, or polymerizations used to make very high molecularweight polymers, are especially sensitive to even trace amounts ofpolymerization-debilitating substances. Particular problems are alsoencountered where the polymer has been formed from monomers in thepresence of the oil or the oil has been heated or subjected toprocessing steps, which may have a tendency to depositpolymerization-debilitating impurities in the oil.

Spray-drying is the transformation of feed from a fluid state to a driedparticulate form by spraying the feed into a hot drying medium,typically a hot gas. Spray-drying is widely used to produce a diverserange of products e.g. instant coffee, dried eggs, instant milk,household detergents, pharmaceutical products, pigments, cosmetics,starch, plastics, ceramics, etc. Typical spray-drying equipment, dryingprocedures, etc. are described in detail in known references e.g. “SprayDrying Handbook,” by K. Master, 5th Ed., Longman Scientific, 1991.

Aqueous solutions of water-soluble polymers may be spray dried as inU.S. Pat. Nos. 3,803,111 and 4,892,932. U.S. Pat. Nos. 4,847,309 and4,585,809 disclose processes for spray-drying acrylic polymer-containingemulsions, U.S. Pat. No. 4,798,888 discloses a process for spray-dryinga polysaccharide emulsion, U.S. Pat. No. 4,816,558 discloses a processfor spray-drying an aqueous dispersion of a synthetic resin and U.S.Pat. No. 4,112,215 discloses a process for spray-drying an aqueousdispersion of a copolymer. U.S. Pat. No. 5,025,004 discloses a processfor spray-drying an emulsion of a water-insoluble polymer.

U.S. Pat. No. 4,035,317 teaches that water-in-oil emulsions ofwater-soluble vinyl-addition polymers may be spray dried, under certainconditions, to produce free-flowing, nondusting polymer particles whichrapidly dissolve in water. Powders of polyacrylamide, acrylamide/acrylicacid copolymer, and acrylamide/dimethylaminopropyl methacrylatecopolymers are described therein. The size range of the spray-driedproducts is such that none are smaller than about 325 mesh (about 40microns), at least about 50% are larger than about 120 mesh (about 122microns), and substantially none of the particles are larger than about20 mesh (about 841 microns). These particles do not clump when added towater and dissolve much faster than traditional dry or gel particles ofwater-soluble polymers. When the spray-dried particles are either largeror smaller than this size range, however, they dissolve with difficulty.Although the invention of U.S. Pat. No. 4,035,317 was a significantadvance in the art, a difficulty nevertheless remains with respect tocertain polymers, in that the spray-drying methods of said patent givespolymers whose properties are undesirably changed relative to theemulsion or microemulsion form. Attempts to spray-dry Mannichpolyacrylamides according to the teachings in the art resulted inpolymer powder exhibiting reduced flocculation performance, compared tothat of the corresponding polymers used in the microemulsion form.Furthermore, the viscosities of solutions of the spray-dried productstended to be significantly lower than desired.

Accordingly, there exists a need for a method of recoveringwater-soluble and water-swellable polymers from dispersions,water-in-oil emulsions or water-in-oil microemulsions to produce rapidlydissolving water-soluble polymers without adversely affecting polymerproperties. It would also be advantageous to provide blends of two ormore spray-dried dry polymers and methods for production thereof wherein90% or greater of the particles in the blend are each individuallycomprised of two or more polymers, so that the effect of stratificationon the blend is minimized. There also exists a need for an economicalmethod for producing substantially dry polymers having good handling anddissolution properties. It would also be advantageous to provide methodsfor spray-drying dispersions, water-in-oil emulsions and water-in-oilmicroemulsions which eliminate or reduce undesirable product changes,and enable component recycling or reuse.

A method has now been discovered for producing substantially drywater-soluble and water-swellable vinyl-addition polymers byspray-drying the corresponding polymer dispersion, water-in-oilemulsion, or water-in-oil microemulsion. Surprisingly, novel dry polymerproducts are obtained whose properties and/or performance are notdetrimentally changed by the spray-drying process. Surprisingly,substantially dry polymers produced by methods of the instant inventiontend to have improved stability relative to the correspondingdispersion, water-in-oil emulsion, or water-in-oil microemulsionpolymers. Advantageous blends of two or more spray-dried dry polymersand methods for production thereof are also provided, wherein 90% ormore of the particles in the blend are each individually comprised oftwo or more polymers. Surprisingly, the dissolution and handlingcharacteristics of the spray-dried polymer particles of the instantinvention are improved by agglomeration. Methods of using the instantcompositions of polymer particles and agglomerates in water-treating,paper making, mining, oil, and agricultural industries are disclosed. Infurther embodiments of the invention, the oil phase of the water-in-oilemulsion or water-in-oil microemulsion is recovered, and purified inanother embodiment, said oil phase being surprisingly substantially freeof polymerization-debilitating substances.

All patents, patent applications, books, and articles mentioned hereinare hereby incorporated by reference.

SUMMARY OF THE INVENTION

According to the instant invention, there is provided a process forproducing substantially dry water-soluble or water-swellablevinyl-addition polymer particles comprising (a) spray-drying avinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion into a gas stream with a residence time ofabout 8 to about 120 seconds and at an outlet temperature of about 70°C. to less than 100° C. and (b) collecting resultant polymer particles.

In another embodiment, there is provided a process for producingsubstantially dry water-soluble or water-swellable vinyl-additionpolymer agglomerates comprising (a) spray-drying a vinyl-additionpolymer-containing water-in-oil emulsion or water-in-oil microemulsioninto a gas stream with a residence time of about 8 to about 120 secondsand at an outlet temperature of about 70° C. to about 100° C., (b)collecting resultant polymer particles, and (c) agglomerating saidpolymer particles to form agglomerates.

In another embodiment, there is provided a process for producingsubstantially dry water-soluble or water-swellable polymer particlesfrom a blend, comprising: (a) spray-drying a blend comprised of, or madeby intermixing (i) a first water-soluble or water-swellablevinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion and (ii) a second water-soluble orwater-swellable vinyl-addition polymer-containing dispersion,water-in-oil emulsion or water-in-oil microemulsion, into a gas streamwith a residence time of about 8 to about 120 seconds and at an outlettemperature of about 70° C. to about 150° C. and (b) collectingresultantipolymer particles.

In yet another embodiment, there is provided a process for producingsubstantially dry water-soluble or water-swellable polymer agglomeratesfrom a blend, comprising: (A) spray-drying a blend comprised of, or madeby intermixing, (I) a first water-soluble or water-swellablevinyl-addition polymer-containing water-in-oil emulsion or water-in-oilmicroemulsion and (II) a second water-soluble or water-swellablevinyl-addition polymer-containing water-in-oil emulsion or water-in-oilmicroemulsion, into a gas stream with a residence time of about 8 toabout 120 seconds and at an outlet temperature of about 70° C. to about150° C., (B) collecting resultant polymer particles, and (C)agglomerating resultant polymer particles.

In another embodiment, there is provided a process for producingsubstantially dry water-soluble or water-swellable polymer agglomeratescomprising (a) spray drying a vinyl-addition polymer-containingdispersion, water-in-oil emulsion, or water-in-oil microemulsion (b)collecting resultant polymer particles; and (c) agglomerating saidresultant polymer particles.

In yet another embodiment, there is provided a process for recoveringoil from a water-soluble vinyl-addition polymer-containing dispersion,water-in-oil emulsion, or water-in-oil microemulsion spray dryingprocess, comprising (a) condensing spray-dry process-generated oil andwater to obtain condensed oil and condensed water; and (b) separatingsaid condensed oil from said condensed water, wherein said condensed oilis substantially free of non-gaseous polymerization-debilitatingsubstances.

In still another embodiment, there is provided a process for purifyingspray-dry process-generated oil, comprising (a) spray-drying awater-soluble vinyl-addition polymer-containing dispersion, water-in-oilemulsion, or water-in-oil microemulsion; (b) recovering spray-dryprocess-generated oil to obtain recovered oil; (c) intermixing saidrecovered oil with aqueous liquid to obtain purified oil; and (d)separating purified oil substantially free of non-gaseouspolymerization-debilitating substances.

In a further embodiment, there is provided a process for purifyingspray-dry process-generated oil, comprising (a) spray-drying awater-soluble vinyl-addition polymer-containing-containing water-in-oilemulsion or microemulsion into a gas stream with a residence time ofabout 8 to about 120 seconds and at an outlet temperature of about 70°C. to about 120° C. or at an outlet temperature of about 70° C. to about95° C.; (b) collecting resultant polymer particles; (c) recoveringspray-dry process-generated oil to obtain recovered oil; (d) intermixingsaid recovered oil with aqueous liquid to obtain purified oil; and (e)separating purified oil substantially free of non-gaseouspolymerization-debilitating substances.

In a still further embodiment, there is provided substantially drywater-soluble or water-swellable polymer particles comprised of afunctionalized polymer, or a polymer having pendant groups selected fromthe group consisting of amide, tertiary aminomethyl, quaternizedtertiary aminomethyl, hydroxyl, glyoxal, sulfonate, sulfonate salt,carboxylic acid, carboxylic acid salt, hydroxamic acid, hydroxamic acidsalt, dialkylaminoalkyl(alk)acrylate, dialkylaminoalkyl(alk)acrylatesalts, and quaternized dialkylaminoalkyl(alk)acrylate, said particleshaving a bulk density of about 0.4 grams per cubic centimeter to about1.0 grams per cubic centimeter, as well as substantially drywater-soluble or water-swellable polymer agglomerates resulting from theagglomeration of these particles, and a method of treating suspendedsolids, comprising (a) dissolving, dispersing or intermixingsubstantially dry water-soluble or water-swellable polymer agglomerateswith or in water to form a polymer solution, polymer dispersion, oraqueous mixture, (b) intermixing said polymer solution, dispersion oraqueous mixture with suspended solids, and (c) separating resultantconcentrated solids from resultant aqueous liquid.

Finally, there are provided substantially dry water-soluble orwater-swellable polymer particles made by a process comprising (a)spray-drying a vinyl-addition polymer-containing dispersion,water-in-oil emulsion, or water-in-oil microemulsion into a gas streamwith a particular residence time, preferably in the range of about 8 toabout 120 seconds, and at a particular outlet temperature in the rangeof about 70° C. to less than 100° C. and (b) collecting resultantpolymer particles, said polymer particles having a drying loss lessthan: (i) the drying loss of substantially dry water-soluble orwater-swellable polymer particles made by a process comprising (a)spray-drying said vinyl-addition polymer-containing dispersion,water-in-oil emulsion, or water-in-oil microemulsion into a gas streamwith a residence time of greater than about 120 seconds and at saidparticular outlet temperature and (b) collecting resultant polymerparticles; or (ii) the drying loss of substantially dry water-soluble orwater-swellable polymer particles made by a process comprising (a)spray-drying said vinyl-addition polymer-containing dispersion,water-in-oil emulsion, or water-in-oil microemulsion into a gas streamwith said particular residence time and at an outlet temperature ofgreater than about 100° C. and (b) collecting resultant polymerparticles; or (iii) the drying loss of substantially dry water-solubleor water-swellable polymer particles made by a process comprising (a)spray-drying said vinyl-addition polymer-containing dispersion,water-in-oil emulsion, or water-in-oil microemulsion into a gas streamwith a residence time of greater than about 120 seconds and at an outlettemperature of greater than about 100° C. and (b) collecting resultantpolymer particles, as well as substantially dry water-soluble orwater-swellable polymer agglomerates resulting from the agglomeration ofthese particles, and a method of treating suspended solids, comprising(a) dissolving, dispersing or intermixing substantially drywater-soluble or water-swellable polymer agglomerates with or in waterto form a polymer solution, polymer dispersion, or aqueous mixture, (b)intermixing said polymer solution, dispersion or aqueous mixture withsuspended solids, and (c) separating resultant concentrated solids fromresultant aqueous liquid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the instant invention, vinyl-additionpolymer-containing dispersions, water-in-oil emulsions, and water-in-oilmicroemulsions are sprayed-dried by a suitable means into a largechamber through which a hot gas is blown, thereby removing most or allof the volatiles and enabling the recovery of the dried polymer.Surprisingly, the means for spraying the dispersion, water-in-oilemulsion, or water-in-oil microemulsion into the gas stream are notparticularly critical and are not limited to pressure nozzles havingspecified orifice sizes; in fact, any known spray-drying apparatus maybe used. For instance, means that are well known in the art such rotaryatomizers, pressure nozzles, pneumatic nozzles, sonic nozzles, etc. canall be used to spray-dry the dispersion, water-in-oil emulsion, orwater-in-oil microemulsion into the gas stream. The feed rate, feedviscosity, desired particle size of the spray dried product, dropletsize of the dispersion, water-in-oil emulsion, or water-in-oilmicroemulsion, etc. are factors which are typically considered whenselecting the spraying means. The size and shape of the chamber, thenumber and type of spraying means, and other typical operationalparameters may be selected to accommodate dryer conditions using commonknowledge of those skilled in the art.

Although open cycle spray-dryers may be used, closed cycle spray dryingsystems are preferred. Gas flow may be concurrent, countercurrent ormixed flow, concurrent flow being preferred. The hot gas, or inlet gas,may be any gas that does not react or form explosive mixtures with thefeed and/or spray-dried polymer. Suitable gases used as the inlet gasare gases known to those skilled in the art, including air, nitrogen,and other gases which will not cause undesirable polymer degradation orcontamination, preferably gases containing about 20% or less oxygen,more preferably about 15% or less oxygen. Most preferably, inert gasessuch as nitrogen, helium, etc. that contain about 5% or less of oxygenshould be used.

The dried polymer may be collected by various means such as a simpleoutlet, classifying cone, bag filter, etc., or the polymer may besubjected to further stages of drying, such as by fluid beds, oragglomeration. The means for collecting the dry polymer product is notcritical. The hot gas that remains after substantially all of thepolymer is removed from the feed generally contains volatiles such asoil, water, etc. and may be vented to the atmosphere or recovered,preferably recovered and most preferably thereafter, recycled. The oilis generally recovered from a vinyl-addition polymer-containingdispersion, water-in-oil emulsion, and water-in-oil microemulsionspray-drying process by condensing spray-dry process-generated oil,preferably condensing spray-dry process-generated oil and spray-dryprocess-generated water, and separating condensed or recovered oil fromcondensed water. Said separating is easily accomplished by simplydraining off the lower layer, and/or pumping off the upper layer, aswater and oil are essentially immiscible. The difference in boilingpoints between water and oil may be such that the condenser may beoperated at a temperature so as to only condense the oil, reducing theenergy costs associated with condensing the vaporized water. However, ithas been surprisingly discovered that condensation of both the water andoil may be beneficial, as the recovered or condensed oil is generallysubstantially free of non-gaseous polymerization-debilitatingsubstances. The volatiles are preferably condensed or condensed with aspray condenser. Spray condensers are well-known to those skilled in theart and function by spraying a liquid into hot gas, causing the hot gasto cool and causing the volatile oil, water, etc. contained in the hotgas to condense. The spray condenser may utilize an aqueous liquid,preferably water, more preferably aqueous acid, most preferably aqueousinorganic acid e.g. aqueous sulfuric acid. Polymerization-debilitatingsubstances are those that inhibit or retard polymerization, or act aschain-transfer agents. Polymerization-debilitating chain-transfer agentsmay have chain transfer constants of about 10⁻⁴ or greater. Preferably,the condensed, condensed, or recovered oil contains less than about 0.1%of such polymerization-debilitating substances, more preferably lessthan about 0.05%, by weight based on total weight.

In some cases, recovered oil, which may be condensed or condensed oil,may not be as free of impurities or polymerization-debilitatingsubstances as desired. Recovered oil may be purified by intermixing saidrecovered oil with aqueous liquid to obtain purified oil and separatingsaid purified oil from the resultant aqueous liquid. Oil purified inthis manner is typically substantially free of non-gaseouspolymerization-debilitating substances, and is generally suitable foruse in subsequent polymerizations. Said aqueous liquid is preferablywater, more preferably aqueous acid. Said acid is preferably aninorganic acid, more preferably sulfuric acid. In a preferredembodiment, a vinyl-addition polymer-containing water-in-oil emulsion orwater-in-oil microemulsion is comprised of an oil recovered from apolymer-containing water-in-oil emulsion or water-in-oil microemulsionspray-drying process. Both purified oil and recovered oil may be treatedto remove gaseous polymerization-debilitating substances such asammonia, oxygen, methylchloride, dimethylamine, formaldehyde, etc. byknown means such as by sparging with an inert gas e.g. nitrogen, helium,etc.

On way to determine whether a treated, recovered, or purified oil issubstantially free of non-gaseous polymerization-debilitating substancesis to use a particular oil to prepare a vinyl-additionpolymer-containing dispersion, water-in-oil emulsion, or water-in-oilmicroemulsion which is subsequently spray-dried, and then to recover thecondensed or condensed oil and, optionally, to purify the recovered oil.If the resultant recovered or purified oil is substantially free ofnon-gaseous polymerization-debilitating substances, the molecular weightor solution viscosity of polyacrylamide prepared by polymerizing orcopolymerizing acrylamide in a water-in-oil emulsion or water-in-oilmicroemulsion using said particular oil will generally be substantiallythe same as the molecular weight or solution viscosity of polyacrylamideprepared by polymerizing acrylamide in a dispersion, water-in-oilemulsion or water-in-oil microemulsion using said recovered or purifiedoil, under otherwise substantially identical conditions.

In one embodiment of the instant invention, the level of formaldehyde inthe recovered or purified oil obtained by spray drying a dispersion,water-in-oil emulsion, or water-in-oil microemulsion, preferably aquaternized Mannich poly(alk)acrylamide microemulsion, is typically lessthan one hundred milligrams formaldehyde per kilogram of recovered orpurified oil, preferably less than ten milligrams formaldehyde perkilogram of recovered or purified oil, and most preferably less than onemilligram formaldehyde per kilogram of recovered or purified oil.Formaldehyde may be detrimental to certain types of polymerizationprocesses, so that a very much reduced level of formaldehyde in therecovered or purified oil is a substantial advantage. It is economicallyand environmentally advantageous to recycle the oil for use in otherprocesses, including the same or other polymerization processes. Thelack of oil and certain residual chemical reagents from thepost-reaction step, in particular formaldehyde, in the polymer particlesare also substantial environmental advantages.

There are four interrelated operating parameters in the instantspray-drying process: gas inlet temperature, gas outlet temperature,product volatiles and residence time in the dryer. The outlettemperature generally should be about 150° C. or below, preferably about120° C. or below, more preferably less than 100° C., even morepreferably about 95° C. or below, most preferably about 90° C. or below.The outlet temperature is generally about 70° C. or higher, preferablyabout 75° C. or higher. Therefore, outlet temperatures are generallyabout 70° C. to about 150° C., preferably about 70° C. to about 120° C.,more preferably about 70° C. to less than 100°, even more preferablyabout 70° C. to about 95° C., most preferably about 75° C. to about 90°C. Outlet temperatures below about 70° C. may be suitable in certaininstances, though generally this is less preferred. For instance, at thecost of efficiency, spray drying could be carried out at long residencetimes, high gas flow rates and low outlet temperatures.

Generally, the dryer should be operated at the lowest possible outlettemperature consistent with obtaining a satisfactory product. Tofacilitate operating at the lowest possible operating temperature, thevinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion is preferably comprised of a volatile oil.“Volatile”, for purposes of this invention, means that the boiling pointor upper end of the boiling point range of the oil is about 200° C. orbelow, preferably about 190° C. or below, most preferably about 180° C.or below. Although the use of an oil having a boiling point or upper endof the boiling point range of greater than 200° C. may be acceptable insome cases, the use of a volatile oil allows for spray drying of thevinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion to be carried out at low outlet temperaturesso that polymer degradation is avoided or substantially reduced.Although in theory an oil with a very low boiling point, say roomtemperature or below, would be most preferable to avoid productdegradation, in practice oils with low boiling points in this range may,under some circumstances, be unacceptable for other reasons related tohandling and flammability. Thus, oils having a boiling point within therange from about 70° C. to 190° C., preferably from about 130° C. toabout 185° C., most preferably from about 160° C. to about 180° C. areused. Suitable oils useful herein include any organic hydrocarbonliquids such as halogenated hydrocarbons, aliphatic hydrocarbons,aromatic hydrocarbons, mixtures of aromatic and aliphatic hydrocarbons,etc. usually containing about 6 to about 12 carbon atoms. Preferredexamples of suitable hydrocarbons include perchloroethylene, benzene,xylene, toluene, mineral oil fractions, kerosenes, naphthas, petroleumfractions and the like. A most preferred oil is a material called IsoparG manufactured by Exxon Chemical. Isopar G is a mixture of syntheticisoparaffinic hydrocarbons having a boiling point range of about 160° C.to about 177° C.

The inlet temperature, the feed rate, and the composition of the polymeremulsion may all affect outlet temperatures. These parameters may bevaried to provide a desired outlet temperature. Feed rates are notcritical, and generally will vary depending on the size of the dryer andthe gas flow rate. Inlet gas temperature is less critical than outletgas temperature, and is generally about 140° C. or above, preferablyabout 160° C. or above. The inlet gas temperature is preferably about200° C. or below and more preferably about 180° C. or below. Thus,preferred inlet gas temperature ranges from about 140° C. to about 200°C., more preferably from about 160° C. to about 180° C. Proper inlet gastemperatures tend to avoid product degradation on the high side and toavoid inadequate drying on the low side.

Residence time is a nominal value obtained by dividing the volume of thedryer by the volumetric gas flow. Residence time is generally at leastabout 8 seconds, preferably at least about 10 seconds. Residence time isgenerally no more than about 120 seconds, preferably no more than about90 seconds, more preferably no more than about 60 seconds, and mostpreferably no more than about 30 seconds. Therefore, the general rangeof residence time is about 8 to about 120 seconds, preferably about 10to about 90 seconds, more preferably about 10 to about 60 seconds, andmost preferably about 10 to about 30 seconds. It is known to thoseskilled in the art that longer residence times are to be expected whenlarger dryers are used or when the dryer is run in a less efficientmanner. For instance, at the cost of efficiency, longer residence timeswould be expected at very low inlet temperatures and slow gas flowrates. As a practical matter, the residence times useful in the presentinvention may vary from the values described above, depending on thesize and type of spray dryer used, the efficiency at which it isoperated, and other operational parameters. Thus, residence timesspecified herein may be modified to accommodate dryer conditions usingcommon knowledge of those skilled in the art.

Any water-soluble or water-swellable vinyl-addition polymer-containingdispersion, water-in-oil emulsion or water-in-oil microemulsion may bespray-dried by the processes of the instant invention. For purposes ofthis invention, water-swellable polymers are generally those that havebeen crosslinked to a certain degree, preferably by forming the polymerin the presence of certain amounts of crosslinking or branching agents.Preferably, water-swellable polymers include microbeads of U.S. Pat.Nos. 5,274,055 and 5,167,766. Water-soluble, branched polymers generallyresult when smaller amounts of crosslinking agent are used to formulatethe polymer, as in U.S. patent application Ser. Nos. 08/455,419 and08/462,922. Most preferably, the water-soluble or water-swellablevinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion is as described in U.S. Pat. Nos. 4,956,399;4,956,400; 5,037,881 5,132,023; 5,286,806; 4,767,540; 5,274,055;5,167,766; 5,847,056; U.S. patent application Ser. Nos. 08/455,419; and08/462,922, which are all incorporated herein by reference. Thevinyl-addition polymer content of the dispersion, water-in-oil emulsionor water-in-oil microemulsion is generally about 10% or greater,preferably greater than 15%, more preferably about 17% or greater, andmost preferably 20% or greater, by weight based on total weight.

Preferably, vinyl-addition polymer-containing dispersions, water-in-oilemulsions or water-in-oil microemulsions are comprised of a polymerhaving pendant groups selected from the group consisting of amide,tertiary aminomethyl, quaternized tertiary aminomethyl, hydroxyl,glyoxal, sulfonate, sulfonate salt, carboxylic acid, carboxylic acidsalt, hydroxamic acid, hydroxamic acid salt,dialkylaminoalkyl(alk)acrylate, dialkylaminoalkyl(alk)acrylate salts,and quaternized dialkylaminoalkyl(alk)acrylate. Thus the polymer may beMannich poly(alk)acrylamide, quaternized Mannich poly(alk)acrylamnide,hydroxamated polyacrylamide, esterified (meth)acrylic acid polymer,esterified (meth)acrylic acid copolymer, and hydrolyzed polyacrylamide.Hydrolyzed polyacrylamide may be formed by inadvertent hydrolysis duringproduction, but is preferably post-reacted e.g. deliberately reactedwith acid or base to a degree of hydrolysis of 5 mole % or more,preferably 10 mole % or more, based on total moles of recurring units,most preferably as disclosed in U.S. Pat. No. 5,286,806. The polymer maycontain recurring units selected from the group consisting ofacrylamide, dialkylaminoalkyl(alk)acrylate,dialkylaminoalkyl(alk)acrylate salts, quaternizeddialkylaminoalkyl(alk)acrylate, (meth)aaylic acid, and salts of(meth)acrylic acid. Preferred polymers included (1) a polymer containing10 mole % or more of recurring units having pendant groups selected fromthe group consisting of carboxylic acid and carboxylic acid salt andhaving a standard viscosity of at least about 8.0 cps, (2) a polymercontaining 20 mole % or more of recurring units having pendant groupsselected from the group consisting of carboxylic acid and carboxylicacid salt and having a standard viscosity of at least about 9.0 cps, (3)a polymer containing at least about 1 mole % of tertiary aminomethylgroups, (4) an acrylamide polymer containing at least about 1 mole % ofquaternized tertiary aminomethyl groups, (5) an acrylamide polymercontaining at least about 1 mole % of hydroxamic acid or hydroxamic acidsalt groups, (6) an esterified polymer containing hydroxamic acid groupsand carboxylic acid groups or salts thereof, and (7) an ionic, organic,polymer microbead being less than about 750 nanometers in diameter ifcrosslinked and less than about 60 nanometers in diameter ifnon-crosslinked and water-insoluble, the jonicity of the microbead beingat least about 1%, preferably having 1 mole % or more of recurring unitshaving pendant groups selected from the group consisting of carboxylicacid and carboxylic acid salt. Polymers and copolymers of acrylamide areparticularly preferred.

In a preferred embodiment, the vinyl-addition polymer-containingwater-in-oil emulsion or microemulsion is a Mannich poly(alk)acrylamide-or quaternized Mannich poly(alk)acrylamide-containing water-in-oilemulsion or microemulsion. Mannich polyacrylamide and quaternary Mannichpolyacrylamide water-in-oil microemulsions may be heat treated prior tospray drying according to methods described in U.S. Pat. No. 5,627,260filed Feb. 12, 1993, which is hereby incorporated herein by reference.

The instant invention is of particular value for preparing substantiallydry, functionalized or post-reacted polymers. In many casesfunctionalized polymers are those that may be or have been post-reacted,e.g. a chemical reaction has been performed on the polymer after theformation of the polymer from the corresponding monomers, see e.g. U.S.Pat. No. 4,956,400. The chemical reaction is generally deliberate orpurposeful, and polymers which are inadvertently or indifferentlyreacted e.g. slightly hydrolyzed during the course of production are notgenerally considered to be functionalized. For example, Mannichpoly(alk)acrylamides, quaternized Mannich poly(alk)acrylamides, acid- orbase-hydrolyzed polyacrylamides, hydroxamated poly(alk)acrylamides, etc.are functionalized polymers that are difficult or impossible to preparein solution or gel form. Since the usual means of preparing dry polymersis via a gel or solution polymerization as described above, dispersion,water-in-oil emulsion and water-in-oil microemulsion may be the onlypractical method for the preparation of functionalized or postreactedpolymers.

The water-soluble or water-swellable vinyl-addition polymer-containingdispersions, water-in-oil emulsions or water-in-oil miicroemulsions ofthe instant invention are generally prepared by polymerization of thecorresponding monomers, preferably as described in U.S. Pat. Nos.4,956,399; 4,956,400; 5,037,881; 5,132,023; 5,286,806; 4,767,540;5,274,055; 5,167,766; 5,847,056; and U.S. patent application Ser. Nos.08/455,419; and 08/462,922. The monomers may be polymerized in adispersion, water-in-oil emulsion or water-in-oil microemulsion;water-in-oil emulsion or water-in-oil microemulsion are preferred. Alldispersions, emulsions and microemulsions described herein are inverseor water-in-oil. An emulsion, for purposes of this invention, isgenerally defined as a composition comprising two liquids or phaseswhich are insoluble in each other along with a surfactant, surfactantmixture or emulsifier. A microemulsion, for purposes of this invention,is generally defined as a thermodynamically stable compositioncomprising two liquids or phases which are insoluble in each other alongwith a surfactant, surfactant mixture or emulsifier. Polymeric inversemicroemulsions which contain a continuous oil phase and apolymer-containing discontinuous phase (usually aqueous) are preparedfrom thermodynamically stable monomer microemulsions. Inversemicroemulsions have a narrow droplet size distribution and are usually,but not always, optically transparent. The discontinuouspolymer-containing phase of a microemulsion forms droplets or micelles,which are usually aqueous and usually have a volume average dropletdiameter which is less than about 2500 Å, preferably less than about2000 Å, and most preferably less than about 1000 Å. Some microemulsionsmay have a volume average droplet diameter as large as about 3000 Å.

Water-in-oil emulsions are well-known in the art, see e.g. VanderhoffU.S. Pat. No. 3,284,393. For the purposes of this invention, dispersionsare compositions comprised of polymer beads or droplets that aredispersed in a non-aqueous liquid e.g. oil, generally with reducedsurfactant levels, but generally including other types of stabilizers,as described in e.g. U.S. Pat. Nos. 4,528,321; 4,628,078; and 4,506,062.

Homopolymers and copolymers of the monomers enumerated herein are fullyencompassed by the instant invention. Preferred nonionic monomers arewater-soluble monomers such as (meth)acrylamide, N-vinyl pyrrolidone,N,N-dialkyl(meth)acrylamide, hydroxyalkyl(meth)acrylate,N-vinylformamide and the like. Small quantities e.g. about 10% or less,of other monomers having limited water solubility e.g. methyl acrylate,styrene, methyl methacrylate, acrylonitrile, vinyl acetate, etc. mayalso be used, provided that the resulting polymer is water-soluble orwater-swellable. Generally, water-swellable polymers are crosslinkedpolymers, not polymers containing so many water-insoluble recurringunits that they swell without dissolving in water. Acrylamide andmethacrylamide are especially preferred non-ionic monomers. Although, insome instances, the polymer may contain 80% or even 100% nonionicmonomer, preferably, the polymer contains about 50% or less of nonionicmonomer, preferably about 40% or less, most preferably about 30% orless, by mole based on total moles of polymer repeat units.Water-swellable polymers or water-soluble, branched polymers may beproduced by copolymerization with multifunctional branching agents e.g.methylenebisacrylamide.

Useful cationic monomers include salts and quaternaries ofdialkylaminoalkyl(alk)acrylate and dialkylaminoalkyl(meth)acrylamide,and diallyldialkylammonium halide. Preferred quaternizing agents aremethyl chloride, ethyl chloride, benzyl chloride, dimethylsulfate, anddiethylsulfate. Preferred cationic monomers include the methyl chloridesalt of dimethylaminoethyl(meth)acrylate, the methyl chloride salt ofdimethylaminopropyl(meth)acrylamide, and diallyldimethylammoniumchloride. Preferably, the polymer contains about 5% or more of cationicmonomer, preferably about 10% or more, most preferably about 30% ormore, by mole based on total moles of polymer repeat units.

Useful anionic monomers include (meth)acrylic acid, fumaric acid,crotonic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid,styrenesulfonic acid, and salts thereof. Sodium and ammonium salts arepreferred. Preferred anionic monomers include sodium acrylate, potassiumacrylate, ammonium acrylate, and the sodium salt of2-acrylamido-2-methylpropanesulfonic acid. Generally, the polymerscontain enough of the salt form of the acid such that the polymer iswater-soluble or water-swellable, preferably greater than 50% of theacid monomers are in the salt form, more preferably 60% or greater, byweight based on total weight. Preferably, the polymer contains about 5%or more of anionic monomer, preferably about 50% or more, morepreferably about 70% or more, most preferably about 75% or more, by molebased on total moles of polymer repeat units.

The polymerization may be carried out in the presence of suchconventional additives as are desired. For example, the polymerizationmay contain chelating agents to remove polymerization inhibitors, chaintransfer agents, pH adjusters, initiators and other conventionaladditives. Polymerization of the monomers may be carried out in anymanner known to those skilled in the art. Initiation may be effectedwith a variety of thermal and redox free radical initiators, includingperoxides, e.g. t-butyl peroxide; azo compounds, e.g.azobisisobutyronitrile; inorganic compounds, such as potassiumpersulfate and redox couples, such as ferrous ammonium sulfate/ammoniumpersulfate. A preferred initiator is sodium bromate/sulfur dioxide.Initiator addition may be effected any time prior to the actualpolymerization per se. Polymerization may also be effected byphotochemical irradiation processes, such as ultraviolet irradiation orby ionizing irradiation from a cobalt 60 source.

Surfactants and/or dispersing agents are generally helpful and sometimesnecessary for the formation and continued stability of vinyl-additionpolymer-containing dispersions, water-in-oil emulsions and water-in-oilmicroemulsions. Where spray-drying is contemplated, ongoing stabilitymay not be required, and it may be advantageous to reduce or eliminatethe surfactants and/or dispersing agents. Vinyl-additionpolymer-containing dispersions, water-in-oil emulsions and water-in-oilmicroemulsions may be prepared using little or no surfactants and/ordispersing agent and spray-dried soon thereafter, preferably during theperiod of continued stability. Preferably, the vinyl-additionpolymer-containing dispersions, water-in-oil emulsions and water-in-oilmicroemulsions contain about 2% or less of surfactant and/or dispersingagent, more preferably about 1% or less, by weight based on totalweight. The spray-dried polymer particles made by the processes ofinstant invention preferably contain 6% or less of surfactant and/ordispersing agent, preferably 4% or less.

Substantially dry water-soluble or water-swellable polymer particles maybe produced from a blend by (a) spray-drying a blend comprised of, ormade by intermixing, (i) a first water-soluble or water-swellablevinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion and (ii) a second water-soluble orwater-swellable vinyl-addition polymer-containing dispersion,water-in-oil emulsion or water-in-oil microemulsion, and (b) collectingresultant polymer particles. Preferred blends of water-in-oil emulsionsand water-in-oil microemulsions are disclosed in U.S. Pat. Nos.5,883,181 and 5,763,530.

Blending of water-in-oil emulsions and water-in-oil microemulsions mayadvantageously provide a product with improved performance by e.g.providing a property such as charge or molecular weight that isdifferent from the individual emulsions or microemulsions from which theblend is derived. The different property may result from averaging ofthe properties of the blend components, or occasionally synergisticresults may be observed. For instance, when treating substrates that arethemselves blends or mixtures of various components, each of the blendcomponents may have a specific role in product performance. Accordingly,although two identical water-in-oil emulsions and water-in-oilmicroemulsions could be blended, it generally preferred to blendemulsions or microemulsions that are different from each other e.g.different performance, different charge, different viscosity, differentmolecular weight, different physical form, different chemical identity,different aging characteristics, different costs, etc.

Spray-drying of blends is advantageous because typically 90% or greater,preferably 95% or greater, most preferably substantially all, of theresultant spray-dried polymer particles each individually contains twoor more water-soluble or water-swellable vinyl-addition polymers, sothat stratification effects may be minimized. Spray-drying a blend maybe particularly advantageous when the first water-soluble orwater-swellable vinyl-addition polymer-containing water-in-oil emulsionor water-in-oil microemulsion has a viscosity that is different from theviscosity of the second water-soluble or water-swellable vinyl-additionpolymer-containing water-in-oil emulsion or water-in-oil microemulsion.This is because viscosity generally impacts the particle sizedistribution of the spray dried polymer particles, so that the particlesize distribution of the particles obtained from the first water-in-oilemulsion or water-in-oil microemulsion may be different from theparticle size distribution of the particles obtained from the secondwater-in-oil emulsion or water-in-oil microemulsion. A dry blend of thetwo different polymers is thus likely to exhibit greater stratificationthan a dry blend obtained by spray-drying a blend of the first andsecond water-in-oil emulsions or water-in-oil microemulsions.

In another embodiment of the instant invention, the Mannich andquaternary Mannich polymer particles have, in some cases, substantiallyreduced residual contamination by certain chemical reagents added duringthe functionalization step e.g. formaldehyde, methyl chloride andamines. Typically, the residual level of methyl chloride in the polymerparticles is below 500 parts per million parts (ppm), based on the totalweight of the particles, and preferably below 100 ppm, same basis.Formaldehyde is typically below 2000 ppm and preferably below 1000 ppm,same basis. Individual residual amines, which may be present as theirhydrochloride salts, are typically present at below 20,000 ppm andpreferably below 10,000 ppm, same basis.

With respect to the various spray-dried and agglomerated polymerproducts described herein, the optimum standard viscosity for aparticular polymer is very dependent on the application e.g.flocculation of suspended solids, paper making, oil recovery, mining,etc. For instance, for many applications, it is preferred that thestandard viscosity of the polymer particles be about 1.5 centipoise orgreater, more preferably about 2.0 centipoise or greater, mostpreferably about 2.5 centipoise or greater. However, applications otherthan flocculation may require polymers with standard viscosities higheror lower than those given above. One advantage of the instant inventionis that the standard viscosity of the polymer particles producedaccording to the processes described herein is generally within about15% of the standard viscosity of the corresponding polymer dispersion,water-in-oil emulsion or water-in-oil microemulsion. This indicates thatthe polymers are not substantially altered by the spray-drying process.

Generally, the polymers of the instant invention have a molecular weightof about 100,000 or greater, preferably greater than about 1,000,000;more preferably greater than about 10,000,000, most preferably greaterthan about 20,000,000. The optimum molecular weight or molecular weightrange for a particular polymer is also very dependent on the applicatione.g. flocculation of suspended solids, paper making, oil recovery,mining, etc. For instance, for many flocculent applications, Mannichpolyacrylamide and quaternized derivatives thereof have a molecularweight greater than about 100,000 and preferably greater than about1,000,000. However, applications other than flocculation may requirepolymers with molecular weights higher or lower than those given above.The water-soluble polymers produced by the processes described hereinmay contain small amounts of insoluble polymer. Such small amounts ofinsoluble polymer do not generally affect the performance of the polymerin, for instance, the applications mentioned above. In some cases,water-swellable polymers are desired for applications such as fluidthickening, papermaking, printing ink thickeners, etc.

When produced according to the spray drying processes disclosed herein,polymer particles of the instant invention are generally about 10microns or greater in diameter, preferably about 40 microns or greater,more preferably about 100 microns or greater, most preferably about 200microns or greater. It is preferred that the polymer particles benon-dusting. Dusting and flow problems are typically exacerbated whenthe polymer particles are small, so larger polymer particles aregenerally desirable. However, very large particles may dissolve moreslowly. Therefore, it is generally desirable for the polymer particlesto be about 1200 microns or less in diameter, preferably about 800microns or less in diameter, more preferably about 600 microns or less,most preferably about 400 microns or less. Generally, at least about 90%of the polymer particles range in size from about 10 microns to about1200 microns, preferably at least about 95%, more preferably at leastabout 98%. The size of the polymer particles can be varied somewhat byaltering the operational parameters e.g. spray configuration, emulsionviscosity, feed rate, etc. Particles may be substantially spherical ornon-spherical; “diameter” of a non-spherical particle is the dimensionalong a major axis.

Although in some cases the particles are hollow, porous structureshaving at least one opening in their walls, it has been discovered thatthese features are not always necessary in order to obtain particleshaving desirable properties e.g. fast dissolution times. In many cases,the spray-drying parameters e.g. nozzle type, nozzle size, outlettemperature, etc. needed to produce particles that are hollow, porousstructures having at least one opening in their walls are inconvenientor uneconomical, and it is advantageous to produce particles that lacksome or all of these features.

The particles formed by the spray-drying processes of the instantinvention may be screened to remove an oversize or undersize fraction.Oversize particles may be fragmented by e.g. grinding, whereasundersized particles are generally agglomerated. Sizes may be determinedby methods known to those skilled in the art e.g. sieving, screening,light scattering, microscopy, microscopic automated image analysis, etc.

Surprisingly, the bulk densities of the spray-dried polymer particles ofthe instant invention are generally greater than the bulk densities ofdry polymers prepared by precipitation of the corresponding dispersion,water-in-oil emulsion or water-in-oil microemulsion. Polymer particleshaving greater density may be advantageous because they occupy a smallervolume, resulting in e.g. lower shipping and storage costs. Whereas thedensities of precipitated polymers are usually less than about 0.35grams per cubic centimeter (g/cc), the bulk densities of the spray-driedpolymer particles of the instant invention are generally about 0.35 g/ccor greater, preferably about 0.4 g/cc or greater, more preferably about0.45 g/cc or greater, most preferably about 0.50 g/cc or greater. Thebulk densities of the spray-dried polymer particles of the instantinvention are generally about 1.1 g/cc or less, preferably about 1.0g/cc or less, more preferably about 0.95 g/cc or less, most preferablyabout 0.90 g/cc or less. Therefore, the bulk densities of thespray-dried polymer particles of the instant invention generally rangefrom about 0.35 to about 1.1 g/cc, preferably about 0.4 to about 1.0g/cc, more preferably about 0.45 to about 0.95 g/cc, most preferablyabout 0.50 to about 0.90 g/cc.

Under the conditions of drying set forth herein, the polymer particlesproduced by the processes described herein are substantially dry. Asused to describe the polymer produced herein, “substantially dry”generally means that the polymer contains about 12% or less volatiles,preferably about 10% or less by weight, based on the weight of the spraydried polymer. The polymer generally contains about 2% or morevolatiles, preferably about 5% or more, by weight based on total weight,and most preferably contains from about 8% to about 10% volatiles byweight, same basis. The volatiles are measured by determining the weightloss on drying the polymer product at about 105° C. for about 30minutes.

Substantially dry water-soluble or water-swellable polymer particles ofthe instant invention may be made by a process comprising (a)spray-drying a vinyl-addition polymer-containing water-in-oildispersion, emulsion or water-in-oil microemulsion into a gas streamwith a particular residence time, preferably in the range of about 8 toabout 120 seconds, and at a particular outlet temperature in the rangeof about 70° C. to less than about 100° C. and (b) collecting resultantpolymer particles. These polymer particles are encompassed within theinstant invention when they have a drying loss less than: (i) the dryingloss of substantially dry water-soluble or water-swellable polymerparticles made by a process comprising (a) spray-drying saidvinyl-addition polymer-containing dispersion, water-in-oil emulsion orwater-in-oil microemulsion into a gas stream with a residence time ofgreater than about 120 seconds and at said particular outlet temperatureand (b) collecting resultant polymer particles; or (ii) the drying lossof substantially dry water-soluble or water-swellable polymer particlesmade by a process comprising (a) spray-drying said vinyl-additionpolymer-containing dispersion, water-in-oil emulsion or water-in-oilmicroemulsion into a gas stream with said particular residence time andat an outlet temperature of greater than about 100° C. and (b)collecting resultant polymer particles; or (iii) the drying loss ofsubstantially dry water-soluble or water-swellable polymer particlesmade by a process comprising (a) spray-drying said vinyl-additionpolymer-containing dispersion, water-in-oil emulsion or water-in-oilmicroemulsion into a gas stream with a residence time of greater thanabout 120 seconds and at an outlet temperature of greater than about100° C. and (b) collecting resultant polymer particles. As used herein,“drying loss” is the change in polymer viscosity resulting fromspray-drying, and is not to be confused with “loss on drying,” or LOD,which is a measure of volatiles as described in the Examples. Dryingloss may be expressed as the viscosity before spray drying minus theviscosity after spray drying, divided by the viscosity before spraydrying, and expressed as a percentage by multiplying by 100.

Additional materials such as flow control agents, dust control agents,pH adjusting agents, surfactant, emulsifier, etc. and the like may beadded to the emulsion or microemulsion before or during the spray dryingprocess, or to the polymer particles after the spray drying process, orboth, to enhance the production, distribution, packaging, handling,performance, etc. and the like of the polymer particles.

We have also discovered that mixing, in any order, an acid, base orbuffer with the substantially dry water-soluble polymer particles thatare the product of the spray drying processes described herein, may beadvantageous. A buffer, for the purposes of this invention, is asubstance or blend of substances that, when dissolved in water, gives asolution that resists changes in pH when small amounts of acid or baseare added. Preferably, a buffer contains an acid and a base. Forexample, any solution of a weak acid plus a salt of that acid is abuffer solution. A base, for the purposes of this invention, is asubstance or blend of substances that, when dissolved in pure water,gives a solution with a pH value greater than 7. An acid, for thepurposes of this invention, is a substance or blend of substances that,when dissolved in pure water, gives a solution with a pH value less than7. The addition of an acid, base or buffer to the polymer particles mayenhance the flow properties of the dry polymer particles and adjusts thepH of the solution that the polymer particles are dissolved into so asto enhance the rate of dissolution and performance of the polymerparticles in the desired application. Bases are preferred and buffersare most preferred. Acids, bases and buffers useful in the instantinvention may be solid or liquid, though it is especially preferred touse an acid, base, or buffer that is substantially dry so as to avoidclumping. Substantially dry, when used to describe the acid, base, orbuffer for the purposes of this invention, means that the powdered acid,base, or buffer flows freely. The acid, base, or buffer may be hydratedas long as it flows freely.

Any base known in the art may be used. Suitable powdered bases mayinclude the alkali and alkaline earth metal salts of carbonate,bicarbonate, citrate, phosphate and acetate. Preferred bases may includesodium carbonate, sodium bicarbonate, potassium carbonate, potassiumbicarbonate, sodium acetate, potassium acetate, sodium citrate,potassium citrate, sodium phosphate, potassium phosphate, etc. and thelike. Sodium carbonate and sodium bicarbonate are more preferred, andsodium bicarbonate is most preferred. The mixture of the base and thepolymer particles is such that the base may be incorporated into theinterior of the particles, or may coat the surface of the particles, ormay be distinct from the particles, or any combination thereof.

Any buffer known in the art may be used. Suitable buffers may comprisethe alkali and alkaline earth metal salts of carbonate, bicarbonate,citrate, phosphate and acetate, with the corresponding acid. The mixtureof the buffer and the polymer particles is such that the base may beincorporated into the interior of the particles, or may coat the surfaceof the particles, or may be distinct from the particles, or anycombination thereof. The buffer system KH₂PO₄/Na₂HPO₄ or hydratesthereof is most preferred.

Any acid known in the art may be used. Suitable acids may compriseinorganic acids e.g. hydrochloric acid, nitrous acid, nitric acid,carbonic acid, phosphoric acid, phosphorus acid, sulfurous acid, andsulfuric acid, as well as organic acids e.g. acetic acid, lactic acid,citric acid, formic acid, alkylsulfonic acids, etc. and the like. Acidssuch as KH₂PO₄, NaH₂PO₄ and hydrates thereof are preferred. In instanceswhere a quaternary Mannich polyacrylamide microemulsion is heat treatedby, for example, adjusting the pH to about 3.6 to about 4.8 addingformaldehyde scavenger, adjusting the water content to about 10-45weight percent of polymer and heating the resultant emulsion at fromabout 40° C. to about 80° C. for about 3 to about 20 hours, the acid ispreferably added in addition to and after the heat treating step.

It is preferred to add the acid, base or buffer directly to the polymerparticles. Alternatively, and less preferably, an acid, base or buffermay be dissolved in water or oil to form a solution or slurry and addedto the water-soluble or water-swellable vinyl-additionpolymer-containing dispersion, water-in-oil emulsion or water-in-oilmicroemulsion before spray drying. The solution or slurry of the acid,base or buffer may be spray dried simultaneously or substantiallysimultaneously with the spray drying of the water-in-oil emulsion orwater-in-oil microemulsion, or the acid, base, or buffer may be addeddirectly to the spray dryer while simultaneously or substantiallysimultaneously spray drying the water-in-oil emulsion or water-in-oilmicroemulsion, to form polymer particles which comprise the acid, base,or buffer. In this case, the acid, base, or buffer need not besubstantially dry. Another, also less preferred, way to add one or moreacids, bases, or buffers to the polymer is to add part of the acid,base, or buffer before or during the spray dry process, and part of theacid, base, or buffer, or perhaps a different acid, base, or buffer, tothe resulting polymer particles. The buffer may be formed when a base isadded to an water-in-oil emulsion or water-in-oil microemulsion orpolymer particle which already contains the corresponding acid, or thebuffer may be formed when an acid is added to a water-in-oil emulsion orwater-in-oil microemulsion or polymer particle that already contains thecorresponding base.

The amount of acid, base or buffer to be added to the water-solubleMannich acrylamide or quaternized Mannich acrylamide polymer particlesof the present invention is preferably an amount sufficient to provide asolution pH of from about 5 to about 11, preferably from about 5.5 toabout 9 and most preferably about 6 to about 8, when the particles orparticle compositions are dissolved in water. Regardless of the mannerin which acid, base or buffer is added (i.e., whether added to theemulsion prior to or during spray drying or to the particles after spraydrying) the amount should be such that the resulting solution containingdissolved polymer particles has a pH at least about 5, preferably atleast about 6 and below about 11, preferably a pH below about 8.

It is understood that the pH of the resulting solution will depend onthe pH of the water before the polymer particles are added. Forinstance, in order to produce a preferred pH in the resulting solutionin the range of about 5 to about 9, more base should generally bepresent in the particles if the water is more acidic than if the wateris less acidic. It is likewise understood that the preferred amount ofbase present in the polymer particles may depend on the pH of the waterinto which the polymer particles are to be dissolved. For example, formany waters of moderate acidity, the polymer particles should containabout 0.1% to about 3.5%, based on total weight, of a preferred basesuch as sodium bicarbonate. Generally, the polymer particles may containbase in an amount of at least about 0.05% by weight, preferably at leastabout 0.1% and generally up to about 10.0% preferably up to about 20.0%by weight based on total particle weight More preferably the amount ofbase ranges from about 0.05% to about 5.0%, based on total weight ofparticles. The aforesaid amounts also apply to acids. Similar reasoningis understood concerning the optimum amount of acid; i.e. the presenceof more acid will be preferred in the particles when the water is morebasic than when the water is less basic in order for the solution of thepolymer to have the desired pH. Routine experimentation by one skilledin the art may be used to determine the appropriate amount of acid, baseor buffer for a particular water.

Likewise, the amount of buffer will also depend on the pH of the waterbefore the polymer particles are added. The amount of buffer presentwill tend to affect the ability of the polymer solution to resistchanges in pH. For instance, for a preferred buffer system such asKH₂PO₄/Na₂HPO₄.12H₂O, the buffer should be at least about 0.1%, byweight, and preferably at least about 5%, by weight, of the total weightof the particles. Although it would seem preferable to use as muchbuffer as possible so as to provide the polymer solution with thegreatest ability to resist pH changes, it is also preferable for thepolymer particles to contain as much polymer as possible. Thus, inpractice, the buffer should comprise less than 50%, by weight, of thepolymer particles, and preferably less than 30%, by weight, same basis.Therefore, the buffer should be present in the polymer particles at alevel of at least about 0.05%, generally from about 0.1% to about 50%,by weight, and preferably about 5% to about 30%, by weight, based on thetotal particle weight. The exact amount of buffer depends on the pH ofthe water and how strongly the polymer solution needs to be able toresist changes in pH.

In addition to pH, another factor which tends to influence the rate ofdissolution of the polymer particles and the performance of the polymeris the temperature of the polymer solution or the solution into whichthe polymer particles are dissolved. Therefore, the amount of acid,base, or buffer present in the polymer particles may vary depending onthe temperature of the water into which the polymer is to be dissolved.For instance, quaternized Mannich polyacrylamide tends to dissolve morereadily at higher temperatures, so that a lower pH, such as about 5, maybe desired to dissolve the polymer when the temperature of the water ishigher, such as about 35° C., whereas a pH of about 8 may be preferredif the water temperature is very low, such as about 5° C. It isapparent, therefore, from the foregoing that less base, or more acid,might be preferred at high temperatures than at low temperatures, andthat the selection of buffer will also depend on the temperature.

The particle size of the acid, base, or buffer is not particularlyimportant, and may be varied to optimize the flow properties of themixture with the polymer particles. For instance, a preferred range ofparticle sizes for sodium bicarbonate is from about 10 to about 500microns, more preferably about 50 to about 300 microns. The means foradding and mixing the substantially dry base to the polymer particlesare likewise not critical. Any mechanical mixing means known to thoseskilled in the art for mixing granular solids is suitable.

It has also been discovered that agglomeration of the polymer particlesof the instant invention may improve the flow properties and dissolutiontimes of the polymers. Agglomeration is a known process for increasingparticle size and various methods for agglomerating particles are knownto those skilled in the art, e.g. “Successfully Use Agglomeration forSize Enlargement,” by Wolfgang Pietsch, Chemical Engineering Progress,April 1996, pp. 29-45; “Speeding up Continuous Mixing Agglomeration withFast Agitation and Short Residence Times,” by Peter Koenig, Powder andBulk Engineering, February 1996, pp. 67-84. Known agglomeration methodssuch as natural agglomeration, mechanical agglomeration, tumble orgrowth agglomeration, pressure agglomeration, binderless agglomeration,agglomeration with binders, etc. may be used to agglomerate the polymerparticles of the instant invention. Agglomeration may optionally befollowed by drying e.g. fluid bed drying, to remove binder e.g. water.Pressure agglomeration is preferred, and mechanical agglomeration usinga water binder, followed by fluid bed drying is most preferred.

The agglomerates formed by agglomerating the polymer particles of theinstant invention tend to have improved flow properties and fasterdissolution times when compared to the unagglomerated polymer particles.Preferably, the agglomerates are non-dusting. Flow properties may bemeasured by measuring flow times as described in the Examples.Dissolution rates may be determined by measuring the increase inviscosity of a polymer solution as a function of dissolution time, asdescribed in the Examples. Typically, about 90% of the agglomerates ofthe instant invention have an agglomerate size of about 120 microns orgreater, preferably about 160 microns or greater, more preferably about200 microns or greater, most preferably about 300 microns or greater.Generally, about 90% of the agglomerates have an agglomerate size ofabout 1500 microns or less, preferably about 1200 microns or less, morepreferably about 1100 microns or less, most preferably about 1000microns or less. Thus, about 90%, preferably 95%, of the agglomerateshave a size in the range of about 120 to about 1500 microns, preferablyabout 160 microns to about 1200 microns, more preferably about 200microns to about 1100 microns, most preferably about 300 microns toabout 1000 microns. Usually, at least about 5% of the agglomerates,preferably at least about 10%, most preferably at least about 15%, arelarger than about 900 microns. The agglomerates formed by agglomeratingthe spray-dried particles of the instant invention may be screened toremove an oversize or undersize fraction. Preferably, agglomerateslarger than about 1200 microns and smaller than about 175 microns anremoved by e.g. screening. Oversize agglomerates are generallyfragmented by e.g. grinding, whereas undersized agglomerates aregenerally recycled into the agglomerator.

The bulk density values of the agglomerates of the instant inventiontend to be lower than the bulk density values of the spray-driedparticles from which they are formed. The bulk densities of theagglomerates of the instant invention are generally about 0.35 g/cc orgreater, preferably about 0.4 g/cc or greater, more preferably about0.45 g/cc or greater, most preferably about 0.50 g/cc or greater. Thebulk densities of the agglomerates of the instant invention aregenerally about 1.0 g/cc or less, preferably about 0.95 g/cc or less,more preferably about 0.90 g/cc or less, most preferably about 0.85 g/ccor less. Therefore, the bulk densities of the agglomerates of theinstant invention generally range from about 0.35 to about 1.0 g/cc,preferably about 0.4 to about 0.95 g/cc, more preferably about 0.45 toabout 0.90 g/cc, most preferably about 0.50 to about 0.85 g/cc.

In order to obtain agglomerates of a preferred size, it is preferredthat the polymer particles themselves be of such a size that they areagglomerable. Agglomeration obviously tends to multiply the averageparticle size, so that it is frequently easier to cause large increasesin particle size than it is to cause small increases in particle size.Therefore, to produce agglomerates of a preferred size or size range, itis generally preferred to agglomerate particles that are much smallerthan the desired agglomerate size, rather than particles that are onlyslightly smaller. Agglomerible particles are generally those that may beconveniently agglomerated to produce agglomerates having a preferredsize. It is possible, but less preferred, to agglomerate largerparticles to produce agglomerates that are larger than desired, thenremove the oversize agglomerates as described above.

The substantially dry polymer particles and agglomerates of the presentinvention are generally comprised of the polymer that was contained inthe dispersion, water-in-oil emulsion, or water-in-oil microemulsionthat was spray-dried, as discussed hereinabove. Preferably, thesubstantially dry polymer particles and agglomerates of the presentinvention are comprised of polymer having pendant groups selected fromthe group consisting of amide, tertiary aminomethyl, quaternizedtertiary aminomethyl, hydroxyl, glyoxal, sulfonate, sulfonate salt,carboxylic acid, carboxylic acid salt, hydroxamic acid, hydroxamic acidsalt, dialkylaminoalkyl(alk)acrylate, dialkylaminoalkyl(alk)acrylatesalts, and quaternized dialkylaminoalkyl(alk)acrylate. Polymers andcopolymers of acrylamide are preferred.

In a preferred embodiment, substantially dry water-soluble orwater-swellable polymer particles and agglomerates are comprised of apolymer having 1 mole % or more of recurring units having pendant groupsselected from the group consisting of tertiary aminomethyl, quaternizedtertiary arninomethyl, glyoxal, hydroxamic acid, and hydroxamic acidsalt, based on total moles of recurring units. In another preferredembodiment, substantially dry water-soluble polymer particles andagglomerates are comprised of a polymer having 1 mole % or more ofrecurring units having pendant groups selected from the group consistingof carboxylic acid and carboxylic acid salt, based on total moles ofrecurring units, said polymer having a standard viscosity of about 7.0cps or greater, and in another preferred embodiment, said polymer isfurther comprised of recurring units having pendant alkyl ester groups,wherein said alkyl ester groups contain from about 2 to about 12 carbonatoms. In another preferred embodiment, substantially dry water-solubleor water-swellable polymer particles and agglomerates are comprised ofacrylamide, (meth)acryloxyethyltrimethylammonium chloride, copolymersthereof, and, optionally, branching agent e.g. methylenebisacrylamide,as described in U.S. patent application Ser. No. 08/455,419 and08/462,922.

In another preferred embodiment, substantially dry water-soluble polymerparticles and agglomerates are comprised of a polymer having 10 mole %or more of recurring units having pendant groups selected from the groupconsisting of carboxylic acid and carboxylic acid salt and wherein saidpolymer has a standard viscosity of at least about 8.0 cps, or (b)wherein said polymer contains 20 mole % or more of recurring unitshaving pendant groups selected from the group consisting of carboxylicacid and carboxylic acid salt and wherein said polymer has a standardviscosity of at least about 9.0 cps.

In yet another preferred embodiment, substantially dry water-solublepolymer particles and agglomerates are comprised of an ionic, organic,polymer microbead being less than about 750 nanometers in diameter ifcrosslinked and less than about 60 nanometers in diameter ifnon-crosslinked and water-insoluble, the ionicity of the microbead beingat least about 1%.

The substantially dry polymer particles and agglomerates of the presentinvention generally exhibit improved stability relative to thedispersion, water-in-oil emulsion, or water-in-oil microemulsion fromwhich they were derived. For instance, Table 7 shows the change instandard viscosity as a function of time at 90° C. for spray driedquaternized Mannich polyacrylamide, compared to a quaternized Mannichpolyacrylamide microemulsion from which the spray dried polymer wasderived. The standard viscosity of the microemulsion polymer changedsubstantially as a function of time, whereas the change in standardviscosity for the spray dried polymer was much less. Table 8 shows dataobtained in a similar manner, except that the dry polymer and themicroemulsion polymer were stored at ambient temperature. Once again,the standard viscosity of the microemulsion polymer changedsubstantially as a function of time, whereas the change in standardviscosity for the spray dried polymer was not substantial. In bothcases, at room temperature and at 90° C., it is quite surprising thatthe spray dried polymer shows greater stability, as measured by standardviscosity, than the corresponding polymer contained in themicroemulsion.

Surprisingly, the standard viscosities of the polymer particles andagglomerates that are the product of the process described herein arenot substantially reduced by the spray drying process of the invention.Generally, the standard viscosity values of the polymer particles arenot decreased by greater than about 15% of their initial value,preferably not greater than about 10%, more preferably not greater thanabout 8%, most preferably not greater than about 5%, as a result of thespray drying process, even when the standard viscosity of the polymer inthe polymer-containing water-in-oil microemulsions is observed todecrease quickly at elevated temperatures as described hereinabove. Itis also surprising that the short residence times result in polymerparticles with low volatile levels. Moreover, the residual level of oilin the finely divided polymer particles is typically very low, usuallyless than 1.0% by weight, based on the total weight of the particles,and preferably less than 0.2% by weight, same basis.

The free flowing, substantially dry, water-soluble polymer particles andagglomerates that are the product of the invention described herein maybe used in many applications, such as, for example, solids/liquidsseparation; flocculants for mining operations to recover ore fromslurries; flocculants for water treating to remove suspended impuritiesetc.; in paper making as a flocculant and to aid paper formation e.g.retention aids; in oil recovery industries e.g enhanced oil recovery,treatment of oily wastewater, etc.; in agriculture e.g. soilstabilization or soil conditioning; in biotechnological applicationse.g. treatment of enzyme broths; and in food processing e.g.flocculation of suspended food particles. The polymers of the presentinvention can conveniently be employed e.g. as flocculants in the formof dilute aqueous solutions. These solutions can be prepared byintermixing, dispersing, and/or dissolving the particles in or withwater. Concentrating dispersions of suspended solids is carried out byadding an effective amount of the dilute aqueous solution to thesuspension to produce an effluent of desired characteristics. Forinstance, a preferred method of treating suspended solids comprises (a)dissolving, dispersing, or intermixing substantially dry water-solubleor water-swellable polymer particles or agglomerates in or with water toform a polymer solution, polymer dispersion, or aqueous mixture, (b)intermixing said polymer solution, dispersion or aqueous mixture withsuspended solids, and (c) separating resultant concentrated solids fromresultant aqueous liquid.

The polymer products of this invention are useful in a wide range ofsolid-liquid separations. These polymers may be used in the dewateringof biologically treated suspensions, such as sewage or other municipaland industrial sludges, the drainage of cellulosic suspension such asthose found in paper production, e.g. paper waste, the production ofpaper e.g. retention aids, and the settlement of various organic orinorganic suspensions, i.e. refinery waste, food waste, etc. Likewise,enzyme broths and suspended mineral solids may be treated similarly. Thedose of polymer effective for a particular application is generallyfound by routine experimentation in a manner well-known to those skilledin the art Preferred doses range from about 0.1 parts of polymer permillion (ppm) to about 10,000 ppm, based on the weight of the solidssuspended in the substrate to be treated.

When the particles are produced in such a way that they are notwater-soluble but are instead water-swellable, they may be dispersed inwater to form aqueous mixtures comprised of dispersions ofwater-swellable polymers. Water-swellable polymers may be useful forapplications such as thickening paint, in papermaking e.g. as describedin U.S. Pat. No. 5,274,055 and U.S. Pat. No. 5,167,766, and as printingink thickeners.

The following examples are set forth for illustration purposes only andare not to be construed as limits on the present invention.

Test Procedures

Standard viscosity is the viscosity of a 0.096% solution ofwater-soluble polymer in 1 N sodium chloride at 25° C., at a pH of 8.0for nonionic and anionic polymers and at a pH of 7.0 for cationicpolymers, except where noted. The viscosity was measured by a BrookfieldLVT viscometer with a UL adapter at 60 rpm. The polymer solution beingmeasured was made by preparing a 0.20% solution of polymer in deionizedwater during two hours and then diluting with the appropriate amounts ofdeionized water and sodium chloride.

Volatiles content (% loss on drying; LOD) was determined using aSartorius Model MA30 Moisture Analyzer. The dry polymer sample was driedat a specified temperature either to a constant weight or for aspecified time. A period of 30 minutes at 105° C. provided a reliableand reproducible indicator of product volatiles content. The results arereported at weight percent volatiles based on the total weight.

Water analysis of the volatiles was performed by Karl Fisher titration.Residual oil levels in the dry products were determined by sampleextraction with supercritical carbon dioxide and gas chromatographyanalysis of the extractant. Residual formaldehyde in the recovered oilwas determined by stirring the recovered oil with water for thirtyminutes, then analyzing the water extractant by ion chromatography.

The laboratory spray dryer used in the Examples below was obtainedcommercially. The chamber of the laboratory spray dryer was 760millimeters (mm) in diameter with a 860 mm verticle side and a 65 degreeconical bottom. Norminal gas flow through the dryer was about 180 cubicmeters per hour. The emulsion or microemulsion feed was fed at thecenter of the top of the chamber using a variable speed pump, through atwo-fluid nozzle using air for atomization. The outlet gas temperaturewas controlled by varying the inlet gas temperature and feed rate. Toprovide an inert atmosphere, the dryer was supplied with nitrogen gasfrom a cryrogenic storage tank. The dried polymer product was dischargedthrough the bottom of the dryer cone to a cyclone where the dry productwas removed and collected. Residence time in the dryer was generallyabout 10-15 seconds.

Some spray-drying Examples were performed with a commercial-scale 8.3foot diameter closed cycle spray dryer equipped with a direct contactspray condenser.

Spray-dried polymer particle products were agglomerated using acommercial mechanical agglomerator in conjunction with a 10.76 squarefoot fluid bed dryer. The agglomerator had a vertical shaft and aflexible polymer housing, with a single shaft rotor having 2 or 3 pin orpaddle-type mixing elements that rotated at 1500 to 5200 revolutions perminute (rpm). It was equipped with mechanically driven rollers thatmoved along the flexible polymer housing to prevent accumulation ofmaterial along the walls. The spray-dried product and binder e.g. waterwere fed to the top of the agglomerator; the spray-dried polymer byscrew feeder, and the via spray nozzles. The agglomerates formed byagglomerating the spray-dried polymer particles dropped out of thebottom of the agglomerator and directly into a fluid bed-dryer, wherethe agglomerates were dried to the desired water content. Typicalresidence time in the agglomerator was about two seconds.

The purpose of the funnel flow test is to identify the funnel at whichpolymer particles and agglomerates fail to flow, both uncompacted andcompacted. The funnel flow test is conducted using 5 funnels, numbered1-5, respectively, having the following outlet diameters: 14 mm, 12 mm,8 mm, 5 mm, 3.5 mm. The procedure is followed by starting with funnel 5(oulet 3.5 mm), blocking the outlet, filling the funnel with the polymerto be tested, and unblocking the outlet to allow the polymer to flow. Ifall of the polymer passed through the funnel, the polymer was given ascore of +5. If the polymer failed to flow from the funnel when theoutlet was unblocked, the procedure was repeated with funnel 4, funnel3, etc. until flow was observed. The funnel number was recorded whenflow was not observed. The process was then repeated to determine theflow of compacted polymer, by tapping the funnel about twenty times (orplaced on a suitable vibrating plate) to create compaction. For example,a polymer with a score of +5, +5 flowed through the No. 5 funnel on bothtests, whereas a polymer with a score of +5, 3 flowed through the No. 5funnel uncompacted, but would not flow through the No. 3 funnel whencompacted.

The bulk density of polymer particles and agglomerates was determined byadding the particles or agglomerates to a suitable preweighed measuringcontainer and “tapping” or slightly agitating the container to cause theparticles or agglomerates to settle. The volume of the polymer was thenread from the measuring container, the measuring container weighed, andthe bulk density calculated in units of grams per cubic centimeter(g/cc).

Dissolving times were determined by adding a 0.2 parts of polymerparticles or agglomerates to 99.8 parts of deionized water in a suitablevessel and stirring with a magnetic stir bar. The bulk viscosity of themixture was measured at regular intervals e.g. five or ten minutes,using a Brookfield LVT viscometer with a UL adapter at 60 rpm, until amaximum bulk viscosity was reached, e.g. until no further increase inbulk viscosity was observed. The time to achieve this maximum bulkviscosity was recorded as the dissolving time and was generally no morethan a few hours.

In the following Examples, the quatemized Mannich polyacrylamidemicroemulsions (Cat.PAM) were prepared as in U.S. Pat. No. 4,956,399,except that Isopar G was used as the oil. The hydrolyzed polyacrylamideemulsions were prepared as described in U.S. Pat. No. 5,286,806, exceptthat Isopar G was used as the oil. Highly crosslinked acrylamide/acrylicacid emulsion and microemulsion copolymer microbeads were prepared asdescribed in U.S. Pat. No. 5,274,055, except that Isopar G was used asthe oil. Cationic emulsion copolymers of(meth)acryloxyethyltrimethylammonium chloride and acrylamide, andanionic copolymers of acrylic acid and acrylamide, were prepared byknown methods e.g. Vanderhoff, U.S. Pat. No. 3,284,393, and branchedcationic polymers were prepared as in U.S. patent application Ser. No.08/455,419, except that Isopar G was used as the oil in all cases. Inall cases, the substitution of Isopar G for the other oil was on avolume basis.

Polymer particle and agglomerate sizes were determined by commerciallyavailable light scattering instrumentation and by conventional sievetechniques.

EXAMPLE 1

A quaternized Mannich polyacrylamide microemulsion (Cat.PAM) having aStandard Viscosity of about 2.5 was spray dried in a laboratory spraydryer using a two-fluid nozzle in a nitrogen atmosphere with gas inletand outlet temperatures of 182° C. and 92° C. respectively. Thevolatiles were 7.65% and the residence time was 14 seconds. The StandardViscosity of a solution of the dry product was 2.25 cps, 9.3% less thanthe standard viscosity of a solution of the microemulsion product. Thepolymer particles ranged in size from about 19 to about 900 microns. Thelevel of residuals in the dry product were as follows: formaldehyde: 520ppm; methyl chloride: less than 100 ppm; dimethylamine hydrochloride:3724 ppm; trimethylamine hydrochloride: 6248 ppm; tetramethylammoniumhydrochloride: 5219 ppm.

EXAMPLE 2 (Comparative)

The Cat.PAM of Example 1 was dried on a 12-inch by 18-inch vacuum doubledrum dryer with less satisfactory results. The steam temperature on thedrum was 115° C. and the steam pressure on the drums was 10 psig. Thedrum was operated at 6 revolutions per minute with a drum clearance of0.010 inches and with a vacuum of about 65 mm Hg. The feed rate wasabout 90 pounds of emulsion per hour. The percent volatiles and StandardViscosity are, set forth in Table 1. A comparison of the dry polymerproduced herein to that of Example 1 shows that the Standard Viscositywas significantly reduced using the drum dryer.

TABLE 1 Ex. Emulsion Gas Inlet/Outlet Residence Volatiles PolymerEmulsion Dry Product Standard Change in Standard No. Name Temperature °C. Time, sec. (LOD), % Standard Viscosity, cps Viscosity, cps.Viscosity, % 1 Cat.PAM 182/92 14 7.65 2.48 2.25 −9.3 2C Cat.PAM N/A N/A9.9 2.48 1.98 −20.2 (drum dried) C: Comparative Example

EXAMPLES 3-7

A Cat.PAM having a Standard Viscosity of about 2.5 was spray dried usingan 8.3 foot diameter commercial spray dryer with a rotary (spinningdisk) atomizer. The dryer was operated using air on a once-throughbasis. The various temperatures and residence time conditions used aredescribed in Table 2; residence time was 30 seconds for all of the runs.Product was collected both at the base of the dryer (chamber) and at thedischarge of a cyclone located immediately after the dryer. Table 2 alsoshows the analytical results of Examples 3-7; in each case, polymerproduct from each of the two collection points (chamber and cyclone) wasanalyzed with the results as shown. In each case, the Standard Viscosityof the polymer particles was within 15% of the Standard Viscosity of thecorresponding Cat.PAM.

TABLE 2 Polymer Dry Emulsion Product Change in Ex. Emulsion GasInlet/Outlet Atomizer Collection Volatiles Standard Standard StandardNo. Name Temperature ° C. Speed, rpm Point (LOD), % Viscosity, cpsViscosity, cps. Viscosity, % 3 Cat.PAM 138/86 19,500 chamber 8.59 2.442.45 +0.4 cyclone 9.64 2.44 2.60 +6.6 4 Cat.PAM 178/93 17,100 chamber8.91 2.44 2.44 0 cyclone 9.71 2.44 2.59 +6.2 5 Cat.PAM 181/92 15,800chamber 8.40 2.44 2.40 −1.6 cyclone 9.42 2.44 2.58 +5.7 6 Cat.PAM 173/8115,800 chamber 9.14 2.44 2.40 −1.6 cyclone 10.93 2.44 2.58 +5.7 7Cat.PAM 171/81 13,400 chamber 10.34 2.44 2.38 −2.5 cyclone 10.85 2.442.49 +2.1

EXAMPLES 8-12

A Cat.PAM having a Standard Viscosity of about 2.5 was spray dried usingan 8.3 foot diameter commercial spray dryer with a pressure nozzleatomizer. The dryer was operated as a closed cycle system using nitrogengas. Product was collected at the base of the dryer or chamber. Afterrecovering the polymer, the outlet gas was passed through a directcontact condenser and the resulting aqueous and Isopar G layers wereseparated. The cooled gas was then reheated and returned to the inlet ofthe dryer; a very small fraction was vented. The level of residualformaldehyde in the recovered Isopar G was 0.09 milligrams/kilogram, asmeasured after the completion of the five runs. The quality of therecovered Isopar G was such that it could be recycled and used directlyfor further microemulsion or emulsion polymerizations. Table 3 providesthe various process conditions; the residence time for all runs was 24seconds. The properties of the resulting dry polymer particles are alsoshown in Table 3. One to three samples of the polymer product werecollected for each run and analyzed as shown. In each case, the StandardViscosity of the polymer particles was within 15% of the StandardViscosity of the initial Cat.PAM used to spray dry.

TABLE 3 Polymer Dry Nozzle Emulsion Product Change in Ex. Emulsion GasInlet/Outlet Orifice Volatiles Standard Standard Standard No. NameTemperature ° C. Size, mm Sample # (LOD), % Viscosity, cps Viscosity,cps. Viscosity, %  8 Cat.PAM 177/86 1.4 1 9.70 2.49 2.36 −5.2 2 9.642.49 2.16 −13.3  9 Cat.PAM 183/90 1.3 1 11.76 2.49 2.57 +3.2 2 11.672.49 2.48 −0.4 3 10.28 2.49 2.46 −1.2 10 Cat.PAM 184/91 1.3 1 8.12 2.492.20 −11.7 11 Cat.PAM 145/91 0.8 1 9.15 2.49 2.21 −11.2 2 9.57 2.49 2.42−2.8 12 Cat.PAM 164/93 1.04 1 6.80 2.49 2.32 −6.8 2 8.53 2.49 2.30 −7.6

EXAMPLE 13

A Cat.PAM having a Standard Viscosity of about 2.5 was buffered withurea/lactic acid to pH 4.5, then heat treated by heating to 67-70° C.for 7-9 hours, then allowed to cool to ambient temperature. This heattreatment process is described in U.S. patent application Ser. No.08/018,858, filed Feb. 12, 1993. The resulting polymer microemulsion wasthen spray dried in a laboratory spray dryer using a two-fluid nozzle.The various temperatures and residence time conditions used aredescribed in Table 4. As shown in the Table, the Standard Viscosity ofthe polymer particles was within 15% of the Standard Viscosity of thecorresponding heat treated Cat.PAM. The levels of residuals in the dryproduct were as follows: formaldehyde: 510 ppm; methyl chloride: lessthan 100 ppm; dimethylamine hydrochloride: 7500 ppm; trimethylaminehydrochloride: 6928 ppm; tetramethylammonium hydrochloride: 4671 ppm.

TABLE 4 Ex. Emulsion Gas Inlet/Outlet Volatiles Residence PolymerEmulsion Dry Product Standard Change in Standard No. Name Temperature °C. (LOD), % Time, sec. Standard Viscosity, cps Viscosity, cps.Viscosity, % 13 Cat.PAM 200/92 5.6 14 2.51 2.17 −13.5 (heat treated)

EXAMPLE 14

Cat.PAM polymer particles were obtained by the spray drying process ofExample 1. To 97.5 parts of these granules was added 2.5 parts of sodiumcarbonate in a suitable vessel. The vessel was mechanically shaken for30 minutes to form a composition containing substantially dry granulesof quaternized Mannich polyacrylamide and sodium carbonate.

EXAMPLE 15

Particles of Cat.PAM were obtained by the spray drying process ofExample 13 and then sodium carbonate was added according to the processof Example 14. Solutions of the particles were prepared by dissolving0.2 parts of the particles in 100 parts water. The dry particles tookapproximately I hour to dissolve. A sample of the heat treated polymermicroemulsion described in Example 13 was also dissolved in water toproduce a similar polymer concentration. Both polymers were allowed tostir in water for two hours, then were tested for their ability toflocculate suspended solids using a 2.0% solids digested sewage sludge.Approximately 200 parts of the sludge was mixed at about 1000 rpm withvarious amounts of the polymer solutions, ranging from 10 parts to 50parts, for about 5 seconds. Thereafter, the drainage rates of theflocculated solids were measured at 10, 20 and 30 seconds. The polymerproducts both performed equally well in the dose range of 25 to 30pounds of polymer per ton of sludge.

EXAMPLE 16

Particles of Cat.PAM were prepared according to Example 14, except thatsodium bicarbonate was used in place of sodium carbonate. The StandardViscosity of these particles was determined, without adjustment of thepH, to be 2.45 cps. In comparison, the Standard Viscosity (measuredwithout pH adjustment) of particles of Cat.PAM prepared by the procedureof Example 1, which did not contain a base, was measured as 1.3centipoise. Standard Viscosity is known in the art to directly correlatewith polymer performance, e.g., flocculation.

EXAMPLE 17C

A polyacrylamide microemulsion was prepared as follows: To 143.75 partsof Isopar G, 26.28 parts Atlas G-1086 and 6.57 parts Arlacel 83, wereslowly added 172.93 parts of a pH 3.0 aqueous solution containingacrylamide (148.2 parts of 53.3% solution), sodium bromate (1.16 partsof 1% solution), 0.68 parts isopropanol, and ethylenediaminetetraaceteicacid (0.40 parts of 40% solution) with stirring. The resulting monomermicroemulsion was sparged for 40 minutes with nitrogen. SO₂ gas was thenbubbled into the resultant microemulsion and the polymerizationtemperature was kept below 65° C. The resulting product was a clearstable microemulsion having a standard viscosity of 3.07 centipoise.

EXAMPLE 18

The procedure of Example 17C was followed except that Isopar G recoveredby following the process of Examples 8-12 was used in place of the freshIsopar G. The resulting product was a clear stable microemulsion havinga standard viscosity of 3.03 centipoise, virtually the same standardviscosity as was obtained using fresh Isopar G (Example 17C).

EXAMPLES 19-23

A 20% hydrolyzed polyacrylamide emulsion having a polymer solids of23.8% and a Standard Viscosity of 8.63 centipoise was prepared asdescribed in U.S. Pat. No. 5,286,806, except that Isopar G was used asthe oil, then spray dried in a laboratory spray dryer using nitrogen.The inlet temperature, outlet temperature and feed rate were varied, andthe LOD, Standard Viscosity (SV), and drying loss of the polymerparticle product were measured as shown in Table 5. Smaller dryinglosses were observed at outlet temperatures of less than 100° C.

TABLE 5 Inlet Outlet Feed Rate, LOD, Product Drying No. Temp., ° C.Temp., ° C. ml/min. % SV, cp Loss, % 19 162 82 96 10.2 8.43 2.3 20 16184 64 7.8 8.31 3.7 21 193 96 52 5.6 8.21 4.9 22C 227 115  44 3.6 8.116.0 23C 253 132  36 2.2 7.48 13.3 C: Comparative Example

EXAMPLES 24-36

A series of 13 water-soluble or water-swellable vinyl-addition polymercontaining water-in-oil emulsions and water-in-oil microemulsions wereprepared according to the methods referenced below (except that Isopar Gwas used as the oil), then spray dried in a laboratory spray dryer usingnitrogen, and the results obtained in Table 6 were obtained. HydrolyzedPAM emulsions were obtained by hydrolyzing polyacrylamide (PAM)emulsions as described in U.S. Pat. No. 5,286,806 (Example 24-25).Acrylamide (AMD) and acrylic acid (AA) were emulsion copolymerized toyield AMD/AA emulsions by known methods e.g. Vanderhoff, U.S. Pat. No.3,284,393 (Examples 26-27). A hydroxamated acrylamide polymer with adegree of hydroxamation of about 40% (40% HX emulsion Example 28) wasprepared by the methods of U.S. Pat. No. 4,767,540. Theacrylamide/acrylic acid microbead microemulsion of Example 29 wasprepared by the methods of U.S. Pat. No. 5,274,055. The water-solublepolyacrylate ester emulsion was prepared by the methods of U.S. Pat. No.5,847,056 (Example 30). Acrylamide and acryloxyethyltrimethylammoniumchloride (AETAC) were emulsion copolymerized to yield AMD/AETACemulsions by known methods e.g. Vanderhoff, U.S. Pat. No. 3,284,393(Examples 31-34); small amounts e.g. about 4 molar parts per million,based on monomers, of methylenebisacrylamide were added to the AMD/AETACpolymers of Examples 32 and 34 to create branching, see e.g. U.S. patentapplication Ser. No. 08/455,419. Mannich and quaternized Mannichmicroemulsions were prepared by the methods of U.S. Pat. No. 4,956,399(Examples 35 and 36). In each case, substantially dry, free flowingmixtures of polymer particles having drying losses of about 15% or lesswere obtained.

TABLE 6 Standard Feed Inlet Outlet Dry Dry Ex. Viscosity Rate, Temp.,Temp., Product Product Drying No. Type Solids (cP) ml/min ° C. ° C. LOD,% SV, cP Loss, % 24 10% hydrolyzed PAM emulsion 24.5 7.51 60 164 85 5.67.34 2.2 25 40% hydrolyzed PAM emulsion 22.2 10.63 52 165 84 6.5 10.392.3 26 70/30 AMD/AA emulsion 34.9 7.94 80 165 86 9.0 8.22 0.6 27 20/80AMD/AA emulsion 34.7 9.30 96 162 87 6.0 8.82 5.2 28 40% HX emulsion 10.612.6 45 174 88 6.1 11.4 9.5 29 40/60 AMD/AA microbead microemulsion 28.01.34 40 189 92 5.0 1.40 4.5 30 Polyacrylate ester emulsion 19.3 7.9 60166 85 6.7 7.43 5.9 31 90/10 AMD/AETAC emulsion 37.1 4.07 80 159 85 5.13.81 6.4 32 60/40 AMD/AETAC branched emulsion 37.8 1.77 95 171 88 4.91.77 0 33 45/55 AMD/AETAC emulsion 47.0 3.60 160 169 81 10.4 3.65 1.4 3445/55 AMD/AETAC branched emulsion 45.3 3.39 96 161 88 5.7 3.39 0 35Mannich microemulsion 23.6 3.42 88 152 82 10.8 3.39 0.9 36 QuaternizedMannich microemulsion 29.8 2.6 160 161 84 6.8 2.46 5.4

EXAMPLE 37-39

A 20% hydrolyzed polyacrylamide emulsion made with Isopar G wasspray-dried on a commercial scale 8.3 foot diameter spray dryer using adirect contact spray condenser. Spray-dry process-generated water andoil were collected and acidified, the layers separated, and the upperIsopar G layer recovered. Side-by-side laboratory-scale acrylamidepolymerizations were then performed using the recovered Isopar G andvirgin Isopar G. The Standard Viscosity of the polyacrylamide made usingthe recovered oil was 6.58 cps, virtually the same as the StandardViscosity of the polyacrylamide made using the virgin oil, 6.67 cps.Subsequently, an acrylamide polymerization was carried out on a200-gallon scale using the same recovered Isopar G and the same recipeas the laboratory scale batch. The resultant polyacrylamide had aStandard Viscosity of 6.55 cP, essentially the same as the laboratorybatch.

EXAMPLES 40-41

A quaternized Mannich polyacrylamnide microemulsion having a StandardViscosity of about 2.1 was spray dried as in Example 1. Both themicroemulsion and the polymer particles were placed into an oven at 90°C., and the Standard Viscosities determined at various times, as shownin Table 7. The decrease in the Standard Viscosity of the microemulsionsample was much greater than the modest decrease observed for thespray-dried polymer, in spite of the relatively severe conditions.

TABLE 7 Example 40 Example 41 C (Comparative) Standard Viscosity ofStandard Viscosity of Time (minutes) Spray-Dried Polymer MicroemulsionPolymer  0 1.86 2.1  15 1.66 1.25 30 1.52 1.15 60 1.47 1.10

EXAMPLES 42-43

A quaternized Mannich polyacrylamide microemulsion having a StandardViscosiity of about 2.5 was spray dried as in Example 1. Both themicroemulsion and the polymer particles were stored at room temperature,and the Standard Viscosities determined at various times, as shown inTable 8. The Standard Viscosity of the spray-dried polymer wasessentially unaffected by the passage of time, whereas the StandardViscosity of the microemulsion polymer decreased noticeably.

TABLE 8 Example 42 Example 43 C (Comparative) Standard Viscosity ofStandard Viscosity of Time (days) Spray-Dried Polymer MicroemulsionPolymer 5 2.25 14 2.44 19 2.48 24 2.36 45 2.11 46 2.44 58 2.09 63 2.3675 1.90 98 2.38 103 1.84 215 2.37 257 1.70

EXAMPLES 44-49

An 20% anionic hydrolyzed PAM emulsion was obtained by hydrolyzing apolycrylamide (PAM) emulsion as described in U.S. Pat. No. 5,286,806. A55% cationic emulsion was obtained by copolymerizing acrylamide andacryloxyethyltrimethylammonium chloride (AETAC) by known methods e.g.Vanderhoff, U.S. Pat. No. 3,284,393. A Cat.PAM was was obtained as inU.S. Pat. No. 4,956,399. In each case, Isopar G was used as the oil.Part of each sample was precipitated in hexane/acetone, then dried undervacuum to produce a polymer powder. Part of each sample was alsospray-dried, and part of each spray-dried sample was agglomerated. Bulkdensity, flow properties (funnel flow test), dissolving time andparticle size were determined and are shown in Table 9. Particle sizewas determined by light scattering for the precipitated and spray-driedpolymers, and by sieve screening for the agglomerates.

TABLE 9 Bulk Dis- Den- Fun- solving Ex. sity, nel Time, Particle SizeNo. Polymer g/cc Flow min. Distribution 44C 20% Anionic 0.26 1,1 90 90%< 109 microns Precipitated 50% < 42 microns 10% < 8 microns 45 20%Anionic 0.79 1,1 85 90% < 148 microns Spray-dried 50% < 65 microns 10% <27 microns 46 20% Anionic 0.53 4,3 20-25 90% < 850 microns Spray-driedand 50% < 350 microns Agglomerated 10% < 170 microns 47C 55% Cationic0.30 1,1 80 90% < 18 microns Precipitated 50% < 11 microns 10% < 5microns 48 55% Cationic 0.86 1,1 60-65 90% < 156 microns Spray-dried 50%< 68 microns 10% < 22 microns 49 55% Cationic 0.52 4,3 25-30 90% < 1500microns Spray-dried and 50% < 600 microns Agglomerated 10% < 260 microns50C Cat.PAM 0.164 1,1 80 90% < 58 microns Precipitated 50% < 27 microns10% < 17 microns 51 Cat.PAM 0.86 1,1 60-65 90% < 152 microns Spray-dried50% < 72 microns 10% < 20 microns 52 Cat.PAM 0.52 4,3 25-30 90% < 1600microns Spray-dried and 50% < 560 microns Agglomerated 10% < 280 micronsC: Comparative Example

EXAMPLES 53-55

The agglomerates of Examples 46, 49 and 52 were screened to removeagglomerates larger than about 1190 microns and smaller than about 177microns. The resultant screened agglomerates had improved flowproperties and dissolving times relative to the agglomerates of Examples46, 49 and 52 as shown in Table 10.

TABLE 10 Example Screened Bulk Density, Funnel Dissolving No.Agglomerate g/cc Flow Time, min. 53 20% Anionic 0.5 5,4 20 54 55%Cationic 0.51 5,4 20-25 55 Cat.PAM 0.51 5,4 <15  

EXAMPLES 56-63

Anionic hydrolyzed PAM emulsions were obtained by hydrolyzingpolyacrylamide (PAM) emulsions as described in U.S. Pat. No. 5,286,806,an 80% anionic emulsion was obtained by copolymerizing acrylamide andacrylic acid (AMD/AA) by known methods e.g. Vanderhoff, U.S. Pat. No.3,284,393, and a Mannich microemulsion was obtained as described in U.S.Pat. No. 4,956,399, except that Isopar G was used as the oil in allcases. Each emulsion and microemulsion was spray-dried according to theconditions shown in Table 11. Smaller drying losses and fasterdissolving times were observed when spray-drying was conducted at loweroutlet temperatures.

TABLE 11 Inlet/Outlet Drying Example No. Polymer Temperature, ° C. Loss,% 56 20% Hydrolyzed Anionic 162/82  4.6 PAM emulsion 57 20% HydrolyzedAnionic 253/132 15.4 PAM emulsion 58 40% Hydrolyzed Anionic 162/84  4.0PAM emulsion 59 40% Hydrolyzed Anionic 265/127 18.8 PAM emulsion 6020/80 AMD/AA 163/86  4.8 emulsion 61 20/80 AMD/AA 225/120 14.5 emulsion62 Mannich microemulsion 155/83  6.8 63 Mannich microemulsion 265/13062.5

EXAMPLES 64-65

A blend of a Cat.PAM and a cationic copolymer is prepared as in U.S.patent application Ser. No. 08/157,764, and a cationic polymerdispersion is prepared according to the procedures of U.S. Pat. No.4,506,062 (without distillation), except that Isopar G is used as theoil. The blend and the dispersion are spray-dried in a laboratoryspray-dryer as in Examples 24-36. Substantially dry polymer particlesare obtained, with drying losses of about 15% or less. Greater than 90%of the spray-dried blend particles contain both the Cat.PAM and thecationic copolymer.

We claim:
 1. Spray-dried polymer particles, or agglomerates thereof,comprised of a post-reacted polymer having 1 mole % or more of recurringunits having pendant groups selected from the group consisting oftertiary aminomethyl and quaternized tertiary aminomethyl, wherein saidpolymer particles are porous and have at least one opening in theirwalls.
 2. Polymer agglomerates as claimed in claim
 1. 3. Polymeragglomerates formed from spray-dried polymer particles comprised of awater-soluble polymer having recurring units having pendant groupsselected from the group consisting of carboxylic acid and carboxylicacid salt, wherein said polymer is a hydrolyzed polyacrylamide having adegree of hydrolysis of 10 mole % or more and a standard viscosity of atleast about 8.0 cps.
 4. Polymer agglomerates formed from spray-driedpolymer particles as claimed in claim 3, wherein said polymer particlesare porous and have at least one opening in their walls.
 5. Spray-driedpolymer particles, or agglomerates thereof, comprised of a water-solublepolymer having pendant groups selected from the group consisting ofhydroxamic acid and hydroxamic acid salt.
 6. Polymer agglomerates asclaimed in claim
 5. 7. Spray-dried polymer particles as claimed in claim5, wherein said polymer particles are porous and have at least oneopening in their walls.
 8. Spray-dried polymer particles, oragglomerates thereof, wherein said polymer is comprised of recurringunits of (meth)acryloxyethyltrimethylammonium chloride ordiallyldimethylammonium chloride, wherein said polymer particles areagglomerable to obtain polymer agglomerates ranging in size from about200 microns to about 1100 microns, or said agglomerates range in sizefrom about 200 microns to about 1100 microns, and wherein said polymerparticles are porous and have at least one opening in their walls. 9.Spray-dried polymer particles, or agglomerates thereof, as claimed inclaim 8, wherein said polymer is comprised of recurring units ofdiallyldimethylammonium chloride.
 10. Polymer agglomerates as claimed inclaim
 8. 11. Spray-dried polymer particles, or agglomerates thereof,wherein said particles are comprised of an ionic, organic, polymermicrobead being less than about 750 nanometers in diameter ifcrosslinked and less than about 60 nanometers in diameter ifnon-crosslinked and water-insoluble, having 1 mole % or more ofrecurring units having pendant groups selected from the group consistingof carboxylic acid and carboxylic acid salt.
 12. Polymer agglomerates asclaimed in claim
 11. 13. Spray dried polymer particles, or agglomeratesthereof, as claimed in claim 11, wherein said polymer particles areporous and have at least one opening in their walls.
 14. Polymeragglomerates as claimed in claim 6, wherein said agglomerates are formedfrom polymer particles which are porous and have at least one opening intheir walls.